Heat stability improvement of hydrocarbon fibers or fabrics

ABSTRACT

The thermal stability of polyolefins is increased by contact with a hydrosulfite.

United States Patent [72] Inventors 122] Filed Dec. 19, 1966 |45| Patented Sept. 21, 1971 [73] Assignee Phillips Petroleum Company [54] HEAT STABILITY IMPROVEMENT 0F HYDROCARBON FIBERS 0R FABRICS 4 Claims, No Drawings [52] US. Cl 117/138.8 E,

8/1i5.6,117/139.5 C1,117/169, 252/86 [51] Int.Cl 006m 11/04 [50] Field of Search 117/1388 E,139.51,138,169;252/8.6;8/115.6;260/45.7 SU 56 I References Cited UNITED STATES PATENTS 2,821,489 1/1958 McNeer et a1. 1l7/i39.5 X 2,879,177 3/1959 Nelson et a1. 117/76 Primary Examiner-Wi1liam D. Martin Assistant Examiner.l. E. Mi1ler,.l|r. Attorney-Young and Quigg ABSTRACT: The thermal stability of polyolefins is increased by contact with a hydrosulfite.

HEAT STABILITY IMPROVEMENT F HYDROCARBON FIBERS 0R FABRICS This invention relates to a process whereby the heat stability of polyolefin fibers or fabrics is improved by treatment with hydrosulfites. In another aspect, the invention relates to a product of the aforementioned process. In another aspect, the invention relates to an article of manufacture comprising a polyolefin fiber or fabric with improved heat stability.

The polymerization of l-olefins to produce polymers capable of utilization in a variety of methods has been pursued quite extensively in recent years. Areas of particular interest are the production of fibers and fabrics utilizing polymerized hydrocarbons. Many hydrocarbon polymers that would have characteristics suitable for use in a variety of products cannot be used in the desired capacity, because of their deformation at elevated temperatures. Of particular interest and concern is the thermal instability of polyolefins. Heat or thermal stability is particularly important in fibers and fabrics that will be subjected to tumble drying at elevated temperatures, to ironing, or to any other high-temperature service or treatment.

In this application the term heat stability" will be taken to refer to the resistance to failure of a polyolefin when heated to elevated temperature. This failure may be observed as a softening and fusion of the fibers or fabrics, or as embrittlement of the fibers or fabric which makes them unsuitable for the intended use.

In one embodiment, the invention comprises the treatment of a polyolefin fiber or fabric, such as polypropylene fibers or fabrics, with a hydrosulfite, such as zinc hydrosulfite, wherein the useful life of the fibers or fabrics is significantly increased due to the resulting increase in heat stability.

Accordingly, an object of the inventive process and product is to produce a polyolefin fiber or fabric with increased heat stability.

Other objects, advantages and features of this invention will be readily apparent to those skilled in the art from the following description and appended claims.

The inventive process of producing a polyolefin fiber or fabric of high-temperature stability through treatment with a hydrosulfite is effected in the instant invention by heating the untreated polymer fiber or fabric, such as polypropylene fibers or fabrics, for a predetermined period of time at a predetermined temperature in a predetermined quantity of aqueous solution containing a predetermined weight percent hydrosulfite.

The polyolefin used in this process comprises polymers and copolymers of aliphatic l-olefins, with less than 8 carbon atoms. This process is particularly applicable to fibers and fabrics of polypropylene. The predetermined period of time is usually about to about 60 minutes. The temperature levels that are most satisfactory are in the range of about 180 F. to about 200 F. The concentration range of hydrosulfite in the aqueous solution can be about I to about 10 weight percent. The ratio of aqueous solution to fiber or fabric can be, by weight, from about 1:1 to about I00: I. Specifically the ratio of 30:1 is entirely satisfactory.

Any hydrosulfite can be used in the inventive process; however, because of the present state of the art, only metallic hydrosulfites, specifically sodium, zinc, and potassium, are widely available. Any of these hydrosuifites, or mixtures thereof, are quite satisfactory. The polyolefin can be treated any time after it has been produced in fiber form; however, it is most economical, in the case of fabrics, to effect the hydrosulfite contact after the fibers have been made into fabric. The treatment of the polymer can be by any means capable of providing for contact between the polymer and the aqueous solution for the prescribed time and at the prescribed temperature. Particularly, contact by immersion is satisfacto- The inventive process and product find applicability in the heat stabilization of fibers or fabrics of polyolefins.

This invention is thus broadly applicable to stabilization of fibers or fabrics of polyolefins through treatment with a hydrosulfite. u

Various modifications of this invention can be made in vlew of the foregoing disclosure and the appended claims without departing from the spirit or scope thereof.

In the specific embodiment of the inventive method presented in the table, staple fibers from four commercial polypropylenes, having melt flows in the range of from 3 to l0 (ASTM D l238-62T, Condition L), were used to demonstrate the process of the invention. Nonwoven bats were made of these staple fibers. These bats were laid on a cotton scrim, needle-punched to the scrim, and the laminate was hot-rolled at about 300 F. to form carpet backing. Samples of the carpet backing were treated by immersion in the indicated aqueous solution for the indicated time at the indicated temperature, rinsed in distilled water, and air-dried. These samples were then placed in an oven at 257 F. and the time for failure, as indicated by flaking of the fiber substance in response to hand rubbing, was measured.

TABLE Hours to FailureBy Hand Rubbing No Treatment Treatment Treatment Treatment Treatment A B C D Polypropylene Type I Type 2 Type 3 Type 4 Ratio ofaqueous solution to fabric, by weight, 30:l.

It is apparent, through reference to the above table, that the use of the immersion treatment of the invention results in an increase in heat stability compared with no treatment, distilled water treatment, and treatment with either acidic or basic solutions. The probative value of the above data are especially significant in view of the fact that treatment D was conducted at only a slightly reduced temperature from that of treatments A, B or C while the temperature of treatment D was in fact maintained for twice the period of time as in treatments A, B or C.

What is claimed is:

1. A process for increasing the thermal stability of polyolefin fibers or fabrics comprising contacting said polyolefin fibers or fabrics with an aqueous solution consisting essentially of from about I to about [l0 weight percent of a metal hydrosulfite for from about 15 minutes to about 60 minutes at a temperature in the range of about 180 F. to about 200 F.

2. The process of claim 1 wherein the hydrosulfite comprises zinc, potassium or sodium hydrosulfite.

3. The process of claim 1 wherein polypropylene fibers or fabrics are contacted by immersion in an aqueous solution of 2 weight percent zinc hydrosulfite; wherein the aqueous solution is then heated to F. over a 30-minute period and held at 190 F. for 30 additional minutes; wherein the ratio of aqueous solution to fiber or fabric is, by weight 30:1.

4. An article of manufacture comprising a polyolefin fiber or fabric treated in accordance with the process of claim 1. 

2. The process of claim 1 wherein the hydrosulfite comprises zinc, potassium or sodium hydrosulfite.
 3. The process of claim 1 wherein polypropylene fibers or fabrics are contacted by immersion in an aqueous solution of 2 weight percent zinc hydrosulfite; wherein the aqueous solution is then heated to 190* F. over a 30-minute period and held at 190 F. for 30 additional minutes; wherein the ratio of aqueous solution to fiber or fabric is, by weight 30:1.
 4. An article of manufacture comprising a polyolefin fiber or fabric treated in accordance with the process of claim
 1. 